Joystick controller

CROSS REFERENCE TO RELATED APPLICATION

This application is a 35 U.S.C. §371 of and claims priority to PCT International Application Number PCT/GB2003/005032, which was filed 19 Nov. 2003, and was published in English, which was based on GB Patent Application No. 0227425.6, which was filed 25 Nov. 2002, the teachings of which are incorporated herein by reference.

The present invention relates to joystick controllers and to methods of assembling joystick controllers.

Joystick controllers are used for a variety of applications requiring local or remote control of movement in multiple directions, such as industrial handling equipment, off-highway vehicles, cranes, closed circuit television (CCTV), leisure simulators, medical equipment and wheelchairs. In many instances these controllers are required to operate in a dirty environment and to endure harsh physical conditions.

A known joystick controller, such as the one described in WO 01/69343, has a joystick mounted in a housing of the controller. The joystick is pivotally mounted within a ball and socket type joint about a pivot point defined by the centre of the ball and socket. The socket is in fixedly mounted to the housing. For two-dimensional control, two yoke members are mounted to the housing such that movement of the joystick causes an angular displacement of the yoke members relative to the housing about respective orthogonal axes. The angular displacement of each of the yoke members is detected by a respective sensor which generates a corresponding output signal.

A problem with this type of joystick is that, for repeatable accurate control, the yokes need to be mounted on axes which intersect at the pivot point or centre. Inaccuracies in the machining and alignment of components can give rise to errors in the output signals.

Accuracy in the output signal is best achieved by the use of a potentiometer having a wiper part attached to the yoke and a stator part attached to the housing. A problem with use of potentiometers is that wear of the wiper and stator parts, or dirt entering these components, can give rise to the generation of noisy signals, thereby affecting accuracy and precise control. In these circumstances equipment may not be usable until the defective potentiometer has been repaired or replaced.

It is an aim of the present invention to provide a joystick controller which alleviates these problems. Further aims of the present invention include providing a joystick controller having a robust construction suitable for use in a harsh environment, and providing an economical and effective method of assembly of a joystick controller.

According to a first aspect the present invention there is provided a joystick controller comprising:

a housing;

a joystick mounted for pivotal movement relative to the housing by means of a ball and socket joint;

a yoke for resolving directional movement of the joystick into a component direction; and

a sensor for sensing movement of the yoke and for generating an output indicative of movement of the joystick in the component direction;

wherein the socket of the ball and socket joint is formed by the yoke.

In an embodiment of the present invention the joystick is mounted for pivotal movement in two dimensions, wherein the controller includes two yokes, preferably orthogonally mounted on the housing with respect to one another for resolving directional movement of the joystick into two component directions. Two sensors, each operative for sensing movement of a respective yoke are provided for generating respective outputs indicative of movement of the joystick in each of the component directions.

It is an advantage that the yokes define the pivot centre of the joystick. In a preferred embodiment, the two yokes are a first yoke member mounted to the housing for pivotal movement about a first axis and a second yoke member mounted to the housing for pivotal movement about a second axis, the pivot centre being where the axes intersect.

A source of alignment error is thereby eliminated. There are also a reduced number of components to be manufactured and assembled, when compared with prior art joysticks, because the yokes together forming the socket.

The housing, first and second yoke members may comprise components manufactured by a die-casting process. Preferably the die-casting process is a high-accuracy pressure die-casting process.

The advantages of using die-cast components are that they provide a rugged construction, have a high dimensional accuracy and avoid the need for subsequent machining operations prior to assembly of the components.

The first yoke member may be mounted to the housing so as to mate or contact with a correspondingly profiled upper surface of a ball member, whereby the members can slidably rotate relative to one another.

The mating surface of the first yoke member is provided with a slot or opening, the joystick extending therethrough from the ball member. The slot/opening is such as to provide for relative rotation of the other yoke member.

The second yoke member may be mounted to the housing so as to mate or contact with a correspondingly profiled lower surface of the ball member for relative slidable rotation. The second yoke member is coupled to the joystick so that movement thereof is such as to pivot the second yoke about the second axis.

The coupling of the joystick to the yoke may be effected by engagement between an extension of the joystick in a slot provided in the second yoke member. The slot is aligned to allow movement of the joystick in a direction parallel to the second axis without engaging the second yoke member and for allowing the joystick to effect movement of the first yoke member.

Mounting the first and second yoke members above and below the ball member respectively ensures that the ball is snugly held between the mating socket surfaces of the yoke members. This arrangement also facilitates assembly of the joystick from one direction without having to turn the joystick over before all the moving components are assembled.

The sensors may each include a sensor element that is carried by a respective yoke member, and a stator element in fixed relationship with the housing, whereby movement of the sensor element relative to the stator element is operable for causing the sensor to produce an output signal.

Each yoke member may carry a further sensor element, a further sensor being provided for producing a further output signal in response to movement of the further sensor element. The first and/or second sensor means may be a potentiometer, the respective sensor element being a wiper of the potentiometer, a stator of the potentiometer being fixed relative to the housing. The further sensor means may be a non-contact sensor, such as a Hall effect sensor with the sensor element being a magnet. It is an advantage that, although less accurate than a potentiometer, a non-contact (e.g. Hall effect) sensor is not susceptible to the generation of noisy signals caused by wear or dirt. Thus, if the output signal from the potentiometer becomes noisy, the output from the non-contact sensor may be used instead. This allows continued operation of the joystick until such time as the defective potentiometer can be repaired or replaced, thereby reducing equipment downtime.

The joystick controller may further include processor means for detecting a predetermined level of deterioration in the output signal generated by the potentiometer, and for automatically generating the output signal by means of the non-contact sensor instead. This arrangement provides the advantage that the less accurate, but wear-resistant non-contact sensor can automatically take over when a potentiometer signal becomes too noisy.

According to a second aspect of the present invention there is provided a method of assembling a joystick controller comprising the components:

a joystick coupled at one end to a ball;

an upper yoke member having a socket portion shaped to receive the ball and having an opening through the shaped portion;

a housing adapted to support the upper yoke member such that the upper yoke member is rotatable about a first axis relative to the housing; and

a clamp member,

the method comprising:

a) locating the upper yoke member into the housing;

b) inserting the joystick through the opening in the upper yoke member so that the ball mates with the shaped portion of the upper yoke member; and

c) securing the clamp member to the housing to hold the assembled components together while allowing the upper yoke member to rotate about the first axis in response to movement of the joystick.

The joystick controller may include a lower yoke member having a socket portion shaped to receive the ball such that the ball is free to rotate within the socket portion. The housing and the support member may be shaped to receive the lower yoke member so that the lower yoke member is free to rotate about a second axis relative to the housing. The method may further include, prior to the step of mounting the support member, the step of locating the lower yoke member into the housing.

It is an advantage that the moveable components of controller (the joystick and the yoke members) are assembled into the housing from one direction without the need to turn the joystick over before the moveable components are secured in place.

Embodiments of the invention will now be described with reference to the accompanying drawings in which:

<figref idref="DRAWINGS">FIG. 1</figref> is a sectional view of a known joystick controller;

<figref idref="DRAWINGS">FIG. 2</figref> shows a housing in an upside down orientation, the housing forming part of a joystick controller according to the present invention;

<figref idref="DRAWINGS">FIG. 3</figref> shows a joystick forming part of the joystick controller of <figref idref="DRAWINGS">FIG. 2</figref>;

<figref idref="DRAWINGS">FIG. 4</figref> shows a part assembly of the joystick controller of <figref idref="DRAWINGS">FIGS. 2 and 3</figref>;

<figref idref="DRAWINGS">FIG. 5</figref> shows a further part assembly of the joystick controller of <figref idref="DRAWINGS">FIGS. 2 to 4</figref>;

<figref idref="DRAWINGS">FIG. 6</figref> shows an exploded view of an assembly of the joystick controller of <figref idref="DRAWINGS">FIGS. 2 to 5</figref>;

<figref idref="DRAWINGS">FIG. 7</figref> is a partial view of the assembled components of <figref idref="DRAWINGS">FIG. 6</figref> in an upright orientation; and

<figref idref="DRAWINGS">FIG. 8</figref> is a view from underneath of the assembly of <figref idref="DRAWINGS">FIG. 7</figref>, including additional components.

Referring to <figref idref="DRAWINGS">FIG. 1</figref>, a known joystick controller has a joystick <b>1</b> mounted to a housing <b>2</b> of the controller. The joystick <b>1</b> is mounted to a ball <b>3</b> of a ball and socket joint, so as to be pivotally moveable about a pivot point <b>4</b>, defined by the centre of the ball <b>3</b>. The socket is defined by a part-spherical surface <b>5</b> formed by machining in the housing <b>2</b>. A first yoke member <b>6</b><i>a </i>is mounted to the housing <b>2</b> such that movement of the joystick <b>1</b> causes an angular displacement of the first yoke member <b>6</b><i>a </i>relative to the housing <b>2</b> about an axis <b>7</b><i>a</i>. The angular displacement of the first yoke member <b>6</b><i>a </i>is detected by a sensor <b>8</b><i>a </i>which generates a corresponding output signal.

For two-dimensional control, a second yoke member <b>6</b><i>b </i>is mounted to the housing <b>2</b> for movement by the joystick <b>1</b> about a second axis <b>7</b><i>b</i>, orthogonal to the first axis <b>7</b><i>a</i>. A second sensor <b>8</b><i>b </i>(not shown) detects angular displacement of the second yoke member <b>6</b><i>b. </i>

For accurate and repeatable control, the first and second axes <b>7</b><i>a</i>, <b>7</b><i>b </i>about which the first and second yoke members <b>6</b><i>a</i>, <b>6</b><i>b </i>pivot, need to be aligned so that they intersect at the pivot point <b>4</b>. Thus, accuracy is required in the machining and assembly of the components.

Referring to <figref idref="DRAWINGS">FIGS. 2 to 6</figref>, components of a joystick controller in accordance with the present invention are shown upside down when compared with the usual orientation in which the joystick is used. This is because the method for assembling the joystick is more readily accomplished in this orientation. As shown in <figref idref="DRAWINGS">FIG. 2</figref>, a housing <b>10</b> is a pressure die-cast component having cast-in features which include a gate <b>50</b> forming an opening through a part-spherical concave surface <b>52</b>, a first pair of part-cylindrical grooves <b>60</b><i>a</i>, <b>60</b><i>b</i>, aligned with a first axis <b>22</b>, and a second pair of part-cylindrical grooves <b>62</b><i>a</i>, <b>62</b><i>b</i>, aligned with a second axis <b>24</b>.

Referring to <figref idref="DRAWINGS">FIG. 3</figref>, a joystick has a cylindrical shaft <b>12</b> coupled at one end to a ball <b>14</b>. The ball <b>14</b> has a part-spherical surface <b>14</b>′. An extension <b>15</b> of the joystick extends from the ball <b>14</b> in an opposite direction to the shaft <b>12</b>. The ball <b>14</b> forms a part of a ball and socket joint of the joystick controller.

<figref idref="DRAWINGS">FIG. 4</figref> shows a part assembly with a first yoke member <b>18</b> located in the housing <b>10</b>. The first yoke member <b>18</b> has a centre portion <b>54</b> between two axially aligned cylindrical shaft portions <b>56</b>, <b>58</b>. The centre portion <b>54</b> is of substantially uniform thickness between a part-spherical convex outer surface <b>54</b><i>a </i>(not visible), and a part-spherical concave inner surface <b>54</b><i>b</i>. The part-spherical outer surface <b>54</b><i>a </i>has a radius slightly smaller than the part-spherical concave surface <b>52</b> in the housing <b>10</b>. The cylindrical shaft portions <b>56</b>, <b>58</b> of the yoke member <b>18</b> are located in the corresponding axially aligned pair of grooves <b>60</b><i>a</i>, <b>60</b><i>b </i>formed in the housing <b>10</b>, so that the first yoke member <b>18</b> is free to rotate about the first axis <b>22</b>.

The part-spherical concave inner surface <b>54</b><i>b </i>of the centre portion <b>54</b> of the first yoke member <b>18</b> is of the same radius as, so as to mate with, the part-spherical convex surface <b>14</b>′ of the ball portion <b>14</b>. A slot <b>64</b> is provided in the centre portion <b>54</b> of the first yoke member <b>18</b> has. The slot <b>64</b> has a width substantially the same size as, and a length substantially greater than the diameter of the joystick shaft <b>12</b> (shown in <figref idref="DRAWINGS">FIG. 3</figref>). In use, the first yoke member <b>18</b> may be urged into pivotal movement about the first axis <b>22</b> by the joystick shaft <b>12</b> bearing against the sides of the slot <b>64</b>. The joystick shaft <b>12</b> is free to move parallel to the length of the slot <b>64</b> when the joystick pivots about the second axis <b>24</b>.

<figref idref="DRAWINGS">FIG. 5</figref> shows a part assembly having the same view as <figref idref="DRAWINGS">FIG. 3</figref>, but with the joystick and a second yoke member <b>20</b> in place. The second yoke member <b>20</b> is of similar construction to the first yoke member <b>18</b>, except that the centre portion <b>70</b> is adapted to fit around an opposing side of the part-spherical surface <b>14</b>′ of the ball portion <b>14</b>. The second yoke member is located in the corresponding axially aligned grooves <b>62</b><i>a</i>, <b>62</b><i>b </i>(see <figref idref="DRAWINGS">FIG. 1</figref>) in the housing <b>10</b> disposed at 90 degrees to the grooves <b>60</b><i>a</i>, <b>60</b><i>b </i>in which the first yoke member <b>18</b> is located. Thus the second yoke member is free to rotate about the second axis <b>24</b>.

The centre portion <b>54</b> of the first yoke member <b>18</b> has an opposed pair of recesses <b>55</b><i>a</i>, <b>55</b><i>b </i>which align with the grooves <b>62</b><i>a</i>, <b>62</b><i>b </i>in which the second yoke member is located. The recesses <b>55</b><i>a</i>, <b>55</b><i>b </i>ensure that the first yoke member is free to rotate without being obstructed by the second yoke member <b>20</b>. Similar recesses <b>69</b><i>a</i>, <b>69</b><i>b </i>are provided in the second yoke member to prevent obstruction by the first yoke member.

The extension <b>15</b> of the joystick extends into a corresponding slot <b>72</b> in the centre portion <b>70</b> of the second yoke member <b>20</b>. In use, the second yoke member <b>20</b> may be urged into pivotal movement about the second axis <b>24</b> by the extension <b>15</b> bearing against the sides of the slot <b>72</b>. The extension <b>15</b> is free to move parallel to the slot <b>72</b> when the joystick pivots about the first axis <b>24</b>.

<figref idref="DRAWINGS">FIG. 6</figref> shows the components of the joystick arranged in an exploded view. The first yoke member <b>18</b> is provided with an arm <b>18</b><i>a</i>, extending radially from the first axis <b>22</b>. Similarly, the second yoke member has an arm <b>20</b><i>a</i>, extending radially from the second axis <b>24</b>. A first sensor element <b>26</b> (not visible in <figref idref="DRAWINGS">FIG. 6</figref>) is provided for mounting to the arm <b>18</b><i>a </i>of the first yoke member <b>18</b> and a second sensor element <b>28</b> is provided for mounting to the arm <b>20</b><i>a </i>of the second yoke member <b>20</b>. The first and second yoke members <b>18</b>, <b>20</b> are each provided with a respective further arm <b>18</b><i>b</i>, <b>20</b><i>b</i>. Further sensor elements (not shown) may be provided for mounting to the further arms <b>18</b><i>b</i>, <b>20</b><i>b</i>. The sensor elements <b>26</b>, <b>28</b> are moving elements of angular position sensors. These may be wipers of potentiometers, or elements of non-contact sensing devices, such as magnets for Hall effect sensors.

The joystick components further comprise a support member <b>30</b> and screws <b>32</b> for mounting the support member by engagement in corresponding threaded holes <b>34</b> in the housing <b>10</b>. The support member <b>32</b> is shaped to support the moveable components when the joystick is turned over to its usual orientation, while allowing the second yoke member <b>20</b> free to pivot on the second axis <b>24</b>.

A further set of screws <b>36</b> is provided for mounting a base member <b>38</b> to the support member <b>30</b>. The base member <b>38</b> is shaped to receive a circuit board <b>40</b> by engagement of holes <b>42</b> in the circuit board <b>40</b> over corresponding collars <b>44</b> on the base member. The circuit board <b>40</b> has connectors <b>46</b> for connection to stator elements (not shown) of angular position sensors which detect the angular displacement of the yoke members <b>18</b>, <b>20</b>. The circuit board <b>40</b> is provided with electronic circuitry <b>48</b> for generating output signals based on the sensed angular positions.

Referring to <figref idref="DRAWINGS">FIG. 7</figref>, where the assembled joystick controller is shown in its normal operational orientation, the joystick shaft <b>12</b> extends through the gate <b>50</b> in the housing <b>10</b>. The joystick shaft <b>12</b> is further provided with a centering arrangement <b>100</b> having a cone piece <b>102</b> slideably mounted on the shaft <b>12</b> and having an enlarged diameter base <b>104</b> adjacent the housing <b>10</b>. A helical spring <b>106</b> surrounds the shaft <b>12</b> and abuts a stop <b>108</b> on the shaft <b>12</b> so as to bias the cone piece <b>102</b> towards the housing <b>10</b>. In use, movement of the joystick shaft <b>12</b> in any direction away from the centre of the gate <b>50</b> causes the base <b>104</b> of the cone piece <b>102</b> to be urged against the biasing action of the spring <b>106</b> so that the cone piece <b>102</b> slides up the shaft <b>12</b>. When the joystick shaft <b>12</b> is released, the biasing action of the spring <b>106</b> against the cone piece <b>102</b> causes the joystick <b>12</b> to return to the centre of the gate <b>50</b>.

<figref idref="DRAWINGS">FIG. 8</figref> is a view from the underside of the assembled components of the joystick controller and shows the attachment of angular position sensors. Mounted on the arm <b>18</b><i>a </i>of the first yoke member <b>18</b> is a carrier <b>118</b> for a first angular position sensor element in the form of a pair of wipers <b>120</b>, <b>22</b> for a potentiometer. The wipers are preferably constructed of an electrically conductive metal having good low friction characteristics. A similar carrier <b>124</b> is mounted to the arm <b>20</b><i>a </i>of the second yoke member <b>20</b> for a second angular position sensor.

The wipers <b>120</b>, <b>122</b> engage a track on a stator part of the first angular position sensor potentiometer mounted to a pillar, which is not shown in <figref idref="DRAWINGS">FIG. 7</figref> for clarity. Angular displacement of the first yoke member <b>18</b> about the first axis <b>22</b> is detected by movement of the wipers <b>120</b>, <b>122</b> along the track so as to effect a change in the electrical resistance of the potentiometer. A similar stator part of the second angular position sensor is mounted to a similar pillar <b>126</b>, shown in <figref idref="DRAWINGS">FIG. 8</figref>. Electrical connections to the potentiometer are made via the pins <b>46</b> on the printed circuit board <b>40</b> engaging in corresponding holes in the pillar <b>126</b>.

A casing (not shown) is provided to enclose the assembly of components underneath the housing <b>10</b>. By making the casing from a metallised material, such as a pressure die-cast zinc alloy, the electronic components inside the casing can be shielded from radio frequency interference.

Referring again to <figref idref="DRAWINGS">FIGS. 2 to 6</figref>, assembly of the joystick can be conveniently performed by the following method steps. <ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0064">a) Locating the first yoke member <b>18</b> into the housing <b>10</b> as shown in <figref idref="DRAWINGS">FIG. 3</figref>.</li><li id="ul0001-0002" num="0065">b) Inserting the joystick shaft <b>12</b> through the slot <b>64</b> in the first yoke member <b>18</b> so that the ball <b>14</b> of the operating shaft <b>12</b> mates with the part-spherical inner surface <b>54</b><i>b </i>of the first yoke member <b>18</b>.</li><li id="ul0001-0003" num="0066">c) Locating the second yoke member <b>20</b> over the ball <b>14</b> of the operating shaft <b>12</b> so that the shaft extension <b>15</b> is located in the slot <b>72</b> and the part-spherical inner surface of the second yoke member mates with the ball <b>14</b>, as shown in <figref idref="DRAWINGS">FIG. 4</figref>.</li><li id="ul0001-0004" num="0067">d) Mounting the support member <b>30</b> to the housing by means of screw fasteners <b>32</b>, so as to hold the assembled components together while leaving the first and second yoke members <b>18</b>, <b>20</b> free to rotate about the first and second axes <b>22</b>, <b>24</b> respectively.</li><li id="ul0001-0005" num="0068">e) Locating the base member <b>38</b> to the support member <b>30</b> by means of screws <b>36</b>.</li><li id="ul0001-0006" num="0069">f) Mounting the printed circuit board <b>40</b> onto the collars <b>44</b> on the base member <b>38</b> and staking the collars <b>44</b> to hold the printed circuit board <b>40</b> in place.</li></ul>

All of the above assembly steps can be accomplished with the joystick controller mounted upside down. Once these assembly steps are complete the moving components are assembled and the joystick can be picked up or turned over to complete the remaining manufacturing steps without any risk of parts becoming dislodged or detached. This eliminates any need to temporarily hold parts together during the assembly process. No special assembly skills are required.